No abstract

En el verano de 2007 se determinó la composición y diversidad de la vegetación arbustiva y arbóreaen cuatro sitios del estado de Nuevo León. El sitio 1 (S1, Bosque Escuela) a una altitud de 1600 m seubicó en el municipio de Iturbide, Nuevo León, México. Los sitios S2 (Crucitas, 550 m), S3 (Campus, 370m) y S4 (Cascajoso, 300 m) se ubicaron en el municipio de Linares, Nuevo León, México. En cada sitiose establecieron aleatoriamente 10 cuadrantes de 10 m x 10 m, en los cuales se estimaron los valoresrelativos de abundancia, dominancia, frecuencia y valor de importancia (VI) de los árboles y arbustospresentes. Además, se determinaron parámetros dasométricos como altura y diámetro de copa. La diversidadde especies para cada sitio se estimó con el índice de Shannon Wiener. La similitud entre sitios sedeterminó con el índice de Jaccard. Se registraron un total de 13 710 individuos pertenecientes a 28familias, predominando los géneros y especies de la familia Leguminosae (10) seguidos por Fagaceae(4), Rutaceae (4), Euphorbiaceae (3), Oleaceae (3), Cupressaceae (3), Rhamnaceae (2) y Verbenaceae(2). Dieciocho familias sólo presentaron una especie. El sitio con el mayor y menor índice de Shannonfueron el Cascajoso (2,08) y Bosque Escuela (1,64), respectivamente. El índice de Jaccard sólo mostróigualdad de especies entre S2, S3 y S4. Las especies de plantas más frecuentes fueron: en S1, Quercuscanbyi, Pinus pseudostrobus y Rhus pachyrrachys (con 11,9%); en S2 Havardia pallens (9,9%); en S3Havardia pallens y Forestiera angustifolia (con 9,8 %) y en S4 Acacia rigidula, Cordia boissieri y Karwinskiahumboldtiana (con 9,8%). Los sitios S2 y S3 presentaron la mayor riqueza específica de especies,posiblemente debido a tener mayor precipitación pluvial.

.mx ( ¶ Autor para correspondencia). RESUMENLa composición química y la fermentación in vitro se determinó en hojas tratadas con y sin polietilén glicol (PEG), de arbustivas nativas del noreste de México como: Acacia amentacea, Celtis pallida, Forestiera angustifolia y Parkinsonia texana colectadas en agostaderos manejados sin disturbio. Las colectas se realizaron en enero y abril de 2009 en tres municipios (China, Linares y Los Ramones) del estado de Nuevo león, México. La composición química y la cinética de la fermentación in vitro variaron ampliamente entre sitios, plantas y entre muestreos dentro de especies. Sólo A. amentacea (18 %) y P. texana (8 %), que tuvieron alto contenido de taninos condensados (TC), aumentaron significativamente los parámetros de producción de gas y la energía metabolizable (EM) después del tratamiento con PEG. Celtis pallida y F. angustifolia tuvieron el más bajo contenido de lignina (LDA) y TC; sin embargo, C. pallida resultó con la más alta fermentación in vitro. Lo anterior se podría explicar por diferencias entre arbustivas respecto a las características genéticas relacionadas con la actividad de los metabolitos secundarios de las plantas. Todas las plantas tuvieron alto valor nutricional para el venado cola blanca debido a que su aparato digestivo tiene mecanismos para neutralizar TC. ABSTRACTThe chemical composition and the in vitro fermentation in leaves, treated with or without polyethylene glycol (PEG), of native shrub from northeastern Mexico, such as: Acacia amentacea, Celtis pallida, Forestiera angustifolia and Parkinsonia texana were established. These shrubs were gathered from fields without any disturbance. Leaves were collected at two sampling times (January and April, 2009) in three municipalities (China, Linares and Los Ramones) of the state of Nuevo Leon, Mexico. A wide range in chemical composition and in vitro gas production kinetics was observed among sites, species and sampling times of each species. A. amentacea (CT = 18 %) and P. texana (8 %), which had a higher condensed tannins content (CT), significantly increased the in vitro gas production parameters and the metabolizable energy after a treatment with PEG. Celtis pallida had the highest in vitro fermentation parameters due to the lower levels of lignin (ADL) and CT. Some variation was observed among shrubs such as in F. angustifolia that had lower fermentation and lower ADL and CT. This discrepancy could be due to genotypic characteristics relative to the type of plant secondary compounds activity. All plants resulted with high nutritional value for white-tailed deer knowing that deer have digestive mechanisms to neutralize CT. PALABRAS CLAVE:Acacia amentacea, Celtis pallida, Forestiera angustifolia, Parkinsonia texana, composición quími-ca, fermentación ruminal.

El objetivo del presente trabajo fue determinar el depósito y la tasa de descomposición de hojarasca de Pinus cooperi en parcelas bajo diferentes intensidades de aclareos (tratamientos) (testigo; T1: Aclareo ligero; T2: Moderado; T3: Fuerte; T4: Severo; T5: Porvenir) en el ejido La Ciudad de Pueblo Nuevo, Durango. Después de un año de observación, la máxima acumulación de hojarasca se registró en el tratamiento Testigo (4.90 Mg ha-1 año-1), seguido por T2 (3.76 Mg·ha-1·año-1), T1 (3.65 Mg·ha-1·año-1), T4 (3.25 Mg·ha-1·año-1) y T3 (3.04 Mg·ha-1·año-1). El menor aporte anual de hojarasca se registró en el T5 (2.58 Mg ha-1 año-1). La tasa de descomposición (k) de la hojarasca se determinó a partir del modelo exponencial de Olson. Las tasas diarias de descomposición fueron mayores durante los primeros 150 días de incubación que en los 210 días subsiguientes. En ambos periodos hubo diferencias significativas entre los tratamientos. Después de 360 días de incubación, la mayor descomposición de hojarasca ocurrió en T3 (42.3 %), independientemente de la densidad residual de las parcelas; en el resto de los tratamientos, la descomposición varió de 30.2 (T1) a 37.1 %(T5). Aun cuando en T3 fue significativamente más rápida que en los demás tratamientos, bajo las condiciones de microclima que ofrecen estos tipos de aclareos, no se detectaron diferencias entre las tasas de descomposición para las cinco condiciones evaluadas en este estudio.

The contents of Cu, Fe, Mn, and Zn were seasonally determined in the leaves of the native shrubs Á Castela erecta, Celtis pallida, Forestiera angustifolia, Lantana macropoda, and Zanthoxylum fagara Á that are browsed by the white-tailed deer (Odocoileus virginianus). The study was conducted at the Tamaulipan thornscrub region, northeastern Mexico, between summer 2004 and spring 2006. Leaf tissues were collected from three county sites (China, Linares, and Los Ramones). Mineral contents were measured using an atomic absorption spectrophotometer. All minerals, in all plants, were significantly different among sites, seasons, and years, as well as the double and triple interactions. In general, plants at the Linares site, that had the highest rainfall, had higher trace element content. Moreover, during the second year, all plant species were higher in micromineral content. Furthermore, during summer were also higher. Regardless of spatiotemporal variations, all plants had suitable levels of Fe and Mn to satisfy the adult range of white-tailed deer requirements. The Cu and Zn presented marginal deficiency in some plants especially during dry seasons (winter and spring). Seasonal variations in minerals could be associated to soil water deficits, excessive irradiance during summer, and extreme low temperatures during winter and spring that could have affected leaf development and micromineral concentrations.

Agave durangensis Gentry biomass, as a residue from the mezcal production process, may be an interesting bioenergy alternative; however, its high ash content limits its application. In this study, pellets were generated with agave fiber mixed with Pinus species sawdust in the following six proportions (%): 100–0 (control), 80–20, 60–40, 40–60, 20–80 and 0–100 (control). The physical, chemical and energetic properties of the pellets were evaluated according to the UNE-EN ISO 17225-6, UNE EN ISO 17827-2, UNE-EN ISO 17828, UNE-EN ISO 18122, UNE-EN ISO 18123, UNE-EN ISO 18125, and UNE-EN ISO 18134-1 standards. The results showed significant statistical differences (p < 0.05) among the treatments tested. The percentage of volatile material and fixed carbon ranged from 86.53 to 89.96% and 4.17 to 8.16%, respectively; the ash content ranged from 0.27 to 10.06%, and the calorific value ranged from 17.33 to 18.03 MJ/kg. Bulk density ranged from 725.76 to 737.37 kg/m3 and the impact-strength index was in the range of 69.33 to 126.66. The mechanical hardness and compressive strength were found to be in the ranges of 50.5 to 68.4% and 0.90 to 36.65 N/mm, respectively. Pellets generated with Agave residue mixture ≤ 40% were identified as promising biobased resources for the sustainable production of renewable energy.

The aim of the study was to determine monthly (2007) the content and deposition of Cu, Fe, Mn and Zn in leaf fallen litterfall samples collected in four sites, northeastern Mexico. Site 1 was located at 1600 m of altitude in a pine forest, mixed with deciduous trees; site 2 was at 550 m in the ecotone of a Quercus spp. forest and submontane scrub; sites 3 and 4 (at 350 m and at 300 m, respectively) were located in the Tamaulipan Thornscrub vegetation. Leaf fallen litterfall samples at each site (2,500 m 2 ) were obtained from ten canisters of 1.0 2 m that were randomly situated at each site. The Cu annual deposition (g ha -1 yr -1 ) was significantly different among sites being higher in site 4 (23.2) and lower in site 1 (4.1). Fe deposition was also significantly higher in site 4 (522.2) and lower in site 1 (120.0). Mn was higher in site 2 (479.4) and lower in site 1 (64.6). Zn was significantly higher in site 1 (62.8) and lower in site 1 (24.3). Micronutrient annual order deposition was as follows: Fe>Mn>Zn>Cu. Differences in deposition may be attributable to environmental conditions and plant species composition at each studied plant community.

What the purpose of having panorama of the nature tourism of the centro ecoturistico Puentecillas, the present study was carriedout, through surveys of visitors and potential tourists from the cities of El Salto and Durango, Durango,the results show that theobjectives of nature tourism are unknown and there is confusion with the different segments such as adventure tourism, ruraltourism and ecotourism has the registration in an ecotourism network, however there are no well-defined products for this segment,there is general information on the forest management program, but it is not updated there are no technical fundamentals of thefocal and complementary elements, only forest inventory information and does not exist a catalog of activities the study potential todevelop activities of ecotourism as workshops of environmental education. Observation of flora and fauna, bird watching, photosafari, interpretive trekking, participation in flora and fauna, rescue programs and camps. The eco-center has a good infrastructureof eco-accommodation, however, there are several services missing, there is also no annual operational plan there is also a lack ofmaintenance of the support elements such as eco-houses, footpaths and viewpoints. The trails lack technical specifications, there areno drainage openings, rainwater channels through which to direct the waters of rain. The ecotourism center presents very littleimplementation of eco technology to manage environmental impacts lack of a vision mission objectives goals programs of workbudget responsible for execution, indicators systems it is important to develop strategies that improve the conditions of the center toplan the growth in a sustainable way.